The invention relates generally to an electrophotographic image forming member and a method and apparatus for forming color images utilizing the image forming member.
Conventional methods of forming electrophotographic images by selectively applying toner to a transfer drum suffer from several drawbacks. These devices utilize poisonous materials and the transfer methods require large, complicated and expensive equipment.
In, IEEE Transactions On Electron Devices, Vol. Ed.-19, No. 4, pp. 396-412 (April 1972), examples of conventional electrophotographic image forming devices are discussed. These devices include inorganic photosensitive material sandwiched between a base and a dielectric layer. This description concerns a method of forming a single color image which includes the use of inorganic photosensitive materials, such as CdS and .alpha.-Se which are toxic materials.
A conventional "transfer drum method" utilizes a single transfer drum to transfer a toner image from the transfer drum to a transfer medium. In this method it is necessary to develop the toner image many times to obtain one color image. The life of the image forming material employed is shorter than the image forming material used for an ordinary monochromatic process. Additionally, positioning the toner with respect to the transfer medium requires very high accuracy and therefore the associated mechanisms are unavoidably complicated.
In another conventional electrophotographic process known as the "lump transfer method", multiple sets of exposing machines and developing machines and repeated developments are required.
Accordingly, it is desireable to develop an improved electrophotographic image forming member and method and an apparatus for practicing the method which avoids the shortcomings of the prior art.